James Roberts Fabio Lepori 2017 <p><span>We used monitoring data from Lake Lugano (Switzerland and Italy) to assess key ecosystem responses to three decades of nutrient management (1983–2014). We investigated whether reductions in external phosphorus loadings (L</span>_ext<span>) caused declines in lake phosphorus concentrations (P) and phytoplankton biomass (Chl </span><i>a</i><span>), as assumed by the predictive models that underpinned the management plan. Additionally, we examined the hypothesis that deep lakes respond quickly to L</span>_ext<span> reductions. During the study period, nutrient management reduced L</span>_ext<span> by approximately a half. However, the effects of such reduction on P and Chl </span><i>a</i><span> were complex. Far from the scenarios predicted by classic nutrient-management approaches, the responses of P and Chl </span><i>a</i><span> did not only reflect changes in L</span>_ext<span>, but also variation in internal P loadings (L</span>_int<span>) and food-web structure. In turn, L</span>_int<span> varied depending on basin morphometry and climatic effects, whereas food-web structure varied due to apparently stochastic events of colonization and near-extinction of key species. Our results highlight the complexity of the trajectory of deep-lake ecosystems undergoing nutrient management. From an applied standpoint, they also suggest that [</span><i>i</i><span>] the recovery of warm monomictic lakes may be slower than expected due to the development of L</span>_int<span>, and that [</span><i>ii</i><span>] classic P and Chl </span><i>a</i><span> models based on L</span>_ext<span> may be useful in nutrient management programs only if their predictions are used as starting points within adaptive frameworks.</span></p> application/pdf 10.1016/j.jglr.2017.01.008 en International Association for Great Lakes Research Effects of internal phosphorus loadings and food-web structure on the recovery of a deep lake from eutrophication article